1. Field of the Invention
The present invention relates generally to signature signals for injection onto magnetic tape and more particularly to an apparatus for injecting a signature signal onto a magentic tape.
2. Description of the Prior Art.
Missile test ranges and other facilities involved in magnetic tape recording, reproducing, or dubbing have experienced difficulty in maintaining uniform levels of data quality.
A magnetic tape recorder signature device provides a means of improving the quality of data recovered from magnetic tape recordings. Crossplay, defined as recording on one machine and reproducing on another, has been identified as a major contributor to data degradation. Although less prevalent, data can be degraded when both recording and reproduction is accomplished on the same machine. The principal reasons for this reduction of data quality are: (1) differences in the alignment of record heads and reproduce heads, (2) improper adjustment of the reproduce electronics, and (3) improper adjustment of the record electronics. A magnetic tape recorder signature device provides a swept-frequency signal which may be recorded on any convenient segment of the tape. Upon playback of the tape, this swept-frequency signal or signature signal may be utilized in adjusting the magnetic tape reproducer for optimum performance. The nature of the reproduced signature may also provide information about improper adjustment or malfunction of the record electronics of the machine on which the original recording was made.
The present invention serves as a standard method of assessing the performance of magnetic tape machines and reducing the occasional catastrophic loss of data caused by crossplay problems. At a minimum, tape signatures on prime data recordings would alert station personnel to the need for repair, adjustment, or maintenance during all phases of tape use including original recording, playback and dubbing operations.
The present method of optimizing reproduced data, if it is done at all, consists of one or two different techniques. It is worth noting that neither of these or any other standard method is used to any extent at this time. The two methods or techniques which may be used are referred to as Lissajous-Pattern and White-Noise methods.
The lissajous pattern method requires the use of a sine wave generator and an oscilloscope to accomplish a single objective which is referred to as reproduce head azimuth alignment. The limitations and disadvantages of this method are that external equipment and special setup is required, the frequency to be recorded must be carefully selected and recorded on two different tracks having definite dimensional spacing, and the indicated result reflecting reproduce head azimuth alignment can be deceiving and ambiguous because the same lissajous pattern can result from either the correct or an incorrect azimuth alignment. In addition, this method is time consuming, unreliable, confusing and provides information relative to reproduce head azimuth alignment only. The method is seldom used because of its complexity.
The white noise method requires the use of a noise generator, band limiting filters, and a spectrum analyzer to achieve its goal relative to signature recording. The limitations and disadvantages of this method are that external equipment and setups are required, and a spectrum analyzer is needed which requires more time and effort to operate than a simple oscilloscope display. The method is seldom used because of its complexity.
The potential user of tape signatures may be unnecessarily discouraged by difficult and time-consuming signature recording procedures such as those discussed above. The difficulty of assembling test equipment, changing patch connections, measuring frequencies, and voltages should be eliminated from the procedure. The types of standardized signatures should be limited to one to simplify and minimize the equipment and training requirements.